Over the last several years, PCs have made more use of pointing devices such as trackballs, pointing sticks, touchpads (or digitizers), styli or mice to increase the useability of computer programs. In particular, computer programs employing graphical user interfaces ("GUIs"), such as Microsoft Windows, make extensive use of pointing devices to access program functions.
Trackballs are characterized by a substantially immobile base adapted to cradle a freely rotatable ball. The ball protrudes from a top surface of the base, allowing a user's palm or fingertips to rotate the ball. Rotation of the ball is translated into X-Y motion (a position parameter) of a pointer on a screen of the PC. Trackballs may be provided with one or more momentary buttons (switches having discrete on and off states) that the user may selectively depress to send commands to the PC. While the trackball has proven to be an effective pointing device, it does suffer from certain disadvantages with respect to portable computers. For instance, the trackball generally requires a large volume to package. This is a distinct disadvantage, particularly in portable computers since space and size is at a premium. In addition, trackballs are usually activated by rollers, which accumulate debris from operation and thus requires frequent cleaning of the rollers.
Pointing sticks feature a more or less vertically-projecting arm that may be deflected in any direction from the vertical. The direction and amount of applied force determines the direction and distance a pointer is moved on the green (again, a position parameter). Pointing sticks are also provided with momentary buttons that the user may selectively depress to send commands to the PC. However, pointing sticks are not very intuitive devices and thus require practice for the user to become proficient in using it. Additionally, over long-term usage, some users develop "numb finger" or "dead digit" due to the excessive pushing forces applied to a basically immobile object.
Touchpads are characterized by a substantially immobile base having a touch-sensitive membranous sensor pad located on a top surface thereof. When a user touches a portion of the pad, the portion either mechanically depresses or registers a change in capacitance, effected by contact with the user, to sense the location on the pad where the user has made contact. Circuitry within the touchpad translates the sensed location into a command to the PC, perhaps causing motion of a pointer (a position parameter) or effecting other, non-position parameter commands (such as emulating clicks of a momentary button).
Some touchpads are pressure sensitive. That is, they are capable of providing a signal representative of the force that the user is bringing to bear on a portion of the touchpad. Still other touchpads are built integrally into the green of the PC (so-called "touch-sensitive" greens). However, such touch-sensitive greens are relatively expensive and delicate and have enjoyed only limited applicability. Furthermore, they tend to suffer from inconsistent operation features, such as "tap mode."
Stylus pointers are pen-like devices characterized by an elongated body in which is located a light sensor. When a user contacts the PC's screen, the light sensor produces a signal when the area of the screen beneath the pen is excited to produce light. Driver software within the PC can determine the location on the screen to which the pen is pointing by determining what area of the screen was excited at the time when the sensor generated the signal. Stylus pointers are not generally supplied with buttons, as they are often limited to entry of position parameters.
Of the above, however, the mouse has, over time, proven to be a fast and efficient pointing device in the PC environment. A mouse is characterized by a movable body that is adapted to traverse the surface of an underlying mousepad. A ball, captured in the body and slightly protruding from a bottom surface of the body, rolls along the surface as the body traverses the same. In a manner similar to that of the trackball, circuitry within the body translates ball rotation into X-Y coordinates employed to move a pointer about the screen. Mice are additionally equipped with one or more momentary buttons (again, switches having discrete on and off states) adapted to be selectively depressed by the user's manual digits. However, there are certain disadvantages associated with the mouse, particularly in a portable computer environment. For example, the over-riding problem with the mouse is that it must be removed for travel, and is a rather large device. Additionally, it suffers from the same cleaning problems the trackball experiences but to a lesser degree.
Accordingly, what is needed in the art is a pointing device that is: 1) relatively small, 2) easy to use, 3) does not need frequent cleaning, 4) inexpensive, 5) intuitive to use, 6) ergonomic such that it does not cause physical strain on the user during repetitive operations and 7) easily and compactly stores within the computer. The pointing device of the present invention addresses the above deficiencies of the prior art.